Why do workflows have to include a marketing email to be able to have goals?

[PaulClappers]

A workflow of mine has as end goal certain tasks. I wanted to report on these created tasks. Apparently, only workflows that include a marketing email, can track goals.  This is what Hubspot has to say about this problem: "only contacts that have also been sent a marketing email in the workflow will count towards the workflow's goal conversion rate.".

Well, this is not very logical...